Wire mounting for an electric fuze of a shaped-charge projectile



United States Patent Oiiee 3,373,687 WIRE MOUNTING FOR AN ELECTRIC FUZE F A SHAPED-CHARGE PROJECTILE Bjrn Herman Olof Simmons, Karlskoga, Sweden, assignor to Aktiebolaget Bofors, Bofors, Sweden, a corporation of Sweden Filed Apr. 6, 1965, Ser. No. 446,006 'Claims priority, application Sweden, Apr. 7, 1964, 4,260/ 64 6 Claims. (Cl. 102-56) The present invention relates to an explosive projectile, and particularly to an explosive projectile of the hollow charge or shaped-charge type, which is detonated by activating an electric fuze.

There are known projectiles of the general kind above referred to in which the fuze proper is mounted in the rear end of the projectile and a contact member is provided at the nose end or in the forward portion of the projectile. The contact member is electrically connected with the Afuze by a conductor wire, and the circuitry of the fuze is so arranged that when the contact member is brought into contact with another metal component of the projectile, an energizing circuit for the fuze is closed. In actual practice, one terminal of the energizing circuit is lusually connected to the outer metal shell casing of the projectile, and the other terminal is connected to the contact member, which is mounted within the casing spaced apart from the outer casing. When the outer casing is deformed due to the projectile striking a target, the casing and the contact member are forced into engagement, thereby closing the energizing circuit.

The mounting of the conductor wire connecting the contact member in the forward portion of the projectile with the fuze in the rear end of the projectile presents several problems, some of which are due to the specific requirements of a shaped or hollow charge, as will be pointed out more fully hereinafter.

The conductor wire must be electrically well insulated from the 'metal casing of the projectile, since, as previously pointed out, this casing is generally used as a conductor. A high grade insulation is of particular importance, since the voltage for activating the fuze is generally supplled by the discharge of a capacitor which is charged, for lnstance, by means of a generator. This generator includes a device for breaking a ma-gnetic field, which is operated by the forces of acceleration to which the projectile is subjected when propelled toward its target. Arrangements of this kind are well known in the art. The capacitance of such capacitor is usually quite small, and accordingly, it is important to reduce leakage losses to a minlmum so that the charge in the capacitor will be suicient to activate the fuze when the energizing circuit thereof is closed as previously described. Obviously, all the components in the activating arrangement for t should `be kept as small as possible for reasons o In other words, maximal utilization is highly important.

Attempts have been made to mount the conductor wire substantially centric, that is, in the lengthwise axis of the hollow charge in the projectile. However, such central location of the wire interferes to a considerable extent with the formation of the high velocity jet of hot particles -which is generated by the shaped charge and which is the purpose of such charge. Tests have shown that the capability of the jet to penetrate the armored or other surface struck by the projectile was reduced to about half of the normal value due to the effect of a centrally arhe fuze f space. of the capacitor charge 3,373,687 Patented Mar. 19, 196s ranged conductor wire, even though the wire was made as thin as was compatible with the required strength of the Wire.

A further problem is caused by the rapid acceleration to which the wire is subjected when the projectile is launched. The diiliculties encountered in this connection are particularly great when the wire is long, since the length of the wire determines the mass of the wire, and hence the effect of the high acceleration or inertia forces acting upon the wire. The high acceleration forces also create difficulties with respect to the mounting of the wire 0n the Contact member, since the point of attachment inherently constitutes a somewhat weakened point.

It has been attempted to solve the problem by embedding at least part of the wire in the char-ge. However, the charges generally used have some electric conductivity, which makes it difficult to maintain a high grade insulation, and the resulting leakage current jeopardizes the safe functioning of the fuz It is a broad object of the invention to provide a novel and improved wire mounting of the general type above referred to which holds the wire in a strong and electrically satisfactory fashion without adversely interfering with the jet stream generated when the charge of the projectile is detonated.

A more specific object of the invention is to provide a novel and improved wire :mounting of the general type above referred to which permits a reduction of the mass of the wire to a minimum value and places the major part of the wire out of the path of the jet stream.

Another more specific object of the invention is to provide a novel and improved wire mounting in which the attachment of the wire to the afore referred to contact member o-f the energizing circuit of the `fuze is such that the wire is fully capable of withstanding the powerful acceleration forces to which it is subjected when the projectile is propelled toward its target.

Other and further objects, features and advantages of the invention will be pointed out hereinafter and set forth in the appended claims constituting part of the application.

In the accompanying drawing a preferred embodiment of the invention is shown by way of illustration, and not by way of limitation.

In the drawing:

FIG. 1 is a perspective view, partly in section, of an explosive projectile of the shaped or hollow charge type in which is incorporated the wire mounting according to the invention; and

FIG. 2 is a detail view on a larger scale showing the attachment of the conductor wire to the contact member in the projectile.

Referring now to the figures in detail, the exemplied projectile is illustrated as an antitank projectile or missile. The front portion of the projectile comprises a substantially conical outer shell 1 which is mechanically and electrically connected to a rear casing 2, which is lled with a shaped explosive charge 3 of suitable composition. The rear end of casing 2 mounts an electric fuze 4 of conventional design. One terminal of the energizing circuit of this fuze should be visualized as being connected to the outer shell 1 through casing 2. A second terminal of the fuze is connected through a conductor wire 5 to a for-ward contact member 6. This contact member is shown in the form of an inner shell substantially duplicating the conical configuration of the outer shell 1. It is mounted spaced apart from the outer shell and electrically insulated therefrom. The circuitry of the fuze is arranged in a conventional manner, so that an energizing circ-uit for the fuze is closed, causing activation thereof, when the outer shell 1 and the inner shell 6 are brought into electric contact with each other, which occurs when the outer shell or both shells are deformed by the impact of the projectile on a target.

The charge .3 is separated from the forward space in the projectile by a generally conical copper liner 7 for the charge, the apex of which faces the fuze. Assuming now that the energizing circuit of the fuze is closed by engagement of the outer shell 1 and the inner shell 6 due to the projectile striking a target, and that the capacitor of the fuze is discharged as a result, the fuze causes ignition of charge .3. As the detonation front proceeds forwardly through the charge, particles of the copper liner 7 are thrown ofir substantially perpendicularly in reference to the surface thereof, and such particles will join to form a jet including extremely hot molten metal particles which move at a high velocity along the lengthwise axis of the projectile. It is known and well understood that the jet defines approximately a cone which has at each transverse plane a diameter of approximately 10% of the diameter of the cavity defined by the liner at the respective plane. The purpose of the jet is to strike and pierce the target at the point where the penetrating force is at a maximum. Such function of hollow or shaped-charge projectiles is well known and understood as such, and does not constitute part of the invention.

As appears from the previous brief explanation of the formation and the path of a jet, a conductor wire centrically disposed in liner 7 is bound to interfere considerably with the formation of the jet. As mentioned before, the penetrating force of the jet may be reduced by about 50%.

By arranging wire eccentrically in reference to the center axis of liner 7, that is, eccentrically in reference to the path of the jet, the wire will not appreciably interfere with the formation of the jet, and is also less exposed to the damaging forces of the jet.

It has been found that the eccentric disposition of the wire in accordance with the invention permits the safe use of blank or uninsulated copper-coated piano wire having a thickness of 0.10 to 0.15 mm.

As is shown in FIG. 1, the wire extends from the fuze through a tube 8 inserted into the charge. The tube may be made of brass or a suitable plastic, but in many instances, a simple bore through the charge is sufficient. A guide disk 9 made, for instance, of insulation material, at the forward end of tube or bore 8 guides the wire which is extended through a hole 6a in the inner contact shell 6. A protective sleeve 10, made, for instance, of plastic, is preferably provided to prevent damage to the wire at the edge of the hole. The portion of the wire protruding between the inner shell 6 and the outer shell 1 is secured to contact shell 6 in strong mechanical and electrical contact therewith. While the wire may be attached by soldering, a rivet 11, such as is shown, has been found to be preferable. To protect the wire further, a strain relief means 12 is preferably provided between the point of attachment of the wire to contact shell l6 at rivet 11 and the hole 6a through which the wire is extended. The strain relief means may be in the form of a headed pin 12 upon which the wire is wound with several turns.

As pointed out before, the diameter of the cone formed by the jet occupies about of the diameter of liner 7 at each transverse plane. As is evident from FIG. 1, the eccentric or slanted mounting of the wire assures that the wire will be outside the jet cone for practically its entire length.

The wire should be kept as short as possible to reduce its mass as much as possible. To this end, the mounting of the wire on inner contact shell 6 is placed as close to the rear end of contact shell 6 as is practical. Obviously, a small mass of the wire, in conjunction with the aforedescribed mounting thereof, and the provision of strain relief means, make the wire capable of withstanding even very high forces of acceleration. It is also essential that the wire be stretched taut so that it offers a minimum basis for attack by the forces of acceleration and that it is safely eccentric for practically its entire length with respect to the path of the jet stream.

While the invention has been described in detail with respect to a certain now preferred example and embodiment of the invention, it will be understood by those skilled in the art, after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention, and it is intended, therefore, to cover all such changes and modifications in the appended claims.

What is claimed is:

1. An explosive projectile with a shaped-charge, said projectile comprising an elongated metal shell; an elongated inner metal shell mounted within the outer shell electrically insulated therefrom and separated by a hollow space, said inner shell being disposed in a forward portion of the outer shell, the side wall of the inner shell being substantially parallel to the side wall of said outer shell portion; an electric fuze mounted in the rear end of said shell, said fuze having two external terminals, an electrically conducting connection between said terminals causing an activation of the fuze, one of said terminals being electrically and mechanically connected to said outer shell; an explosive shaped-charge in the rear portion of said outer shell, a generally conical liner mounted in said rear portion of the outer shell coaxially therewith and lining said charge to define a generally conical hollow space in said rear portion, the apex of the liner facing the fuze; and a conductor wire connecting said inner shell to the other terminal of said fuze, said wire extending tautly stretched through said generally conical space and being eccentrically disposed with respect to the center axis of the liner, metallic contact between said inner shell and said outer shell due to a deformation of at least one of the parallel side walls of the shells causing an electrically conducting connection between the terminals whereby the fuze is activated.

2. An explosive projectile according to claim 1, wherein said conductor wire is an uninsulated wire.

3. An explosive projectile according to claim 1, wherein said conductor wire is extended through a hole in the inner shell near the end thereof facing said fuze, a portion of the wire protruding through said hole being flxedly attached to the inner shell at a point thereof forwardly spaced apart from said hole.

4. An explosive projectile according to claim 3, wherein a strain relief means is provided between said hole in the inner shell and the point of attachment of the wire to the inner shell.

5. An explosive projectile according to claim 4, wherein said strain relief means comprises a headed pin secured to said inner shell, said wire enveloping said pin with at least one turn.

6. An explosive projectile with a shaped-charge, said projectile comprising an elongated outer metal shell; an electric fuze mounted in the rear end of said shell, said fuze having two external terminals, an electrically conJ ducting connection between said terminals causing an activation of the fuze, one of said terminals being electrically and mechanically connected to said outer shell; an explosive shaped-charge in the rear portion of said shell; a generally conical liner mounted in said rear portion of the shell coaxially therewith and lining said charge, the apex of the liner facing the fuze; a contact member mounted in the forward portion of the shell electrically insulated therefrom and separated by a hollow space; and a conductor wire connecting said contact member to the other terminal of said fuze, said wire extending without contact with said explosive charge from said fuze coaxially through an axial bore in said explosive charge to the apex of said liner and from said apex through a hollow space dened by the interior wall of the liner eccentrically with respect to the center axis of the liner so that the major portion of said conductor wire is disposed outside the peripheral outline of an imaginary cone extending within the interior space of said liner coaxially therewith, the diameter of said cone on any transverse plane thereon being more than approximately 10 percent of the inner diameter of the liner in the respective plane, metallic contact between said shell and said contact member due a deformation of the shell o1 the Contact member causing an electrically conducting connection between said terminals whereby the fuze is activated.

References Cited UNITED STATES PATENTS Jordan 102-56 Roberts 102-56 Meister 102-56 Kller et al 102-56 McGinnis 102-702 Olsen 102-70.2

10 BENJAMIN A. BORCHELT, Primary Examiner.

SAMUEL FEINBERG, Examiner.

V. KUJAWA, Assistant Examiner. 

1. AN EXPLOSIVE PROJECTILE WITH A SHAPED-CHARGE, SAID PROJECTILE COMPRISING AN ELONGATED METAL SHELL; AN ELONGATED INNER METAL SHELL MOUNTED WITHIN THE OUTER SHELL ELECTRICALLY INSULATED THEREFROM AND SEPARATED BY A HOLLOW SPACE, SAID INNER SHELL BEING DISPOSED IN A FORWARD PORTION OF THE OUTER SHELL, THE SIDE WALL OF THE INNER SHELL BEING SUBSTANTIALLY PARALLEL TO THE SIDE WALL OF SAID OUTER SHELL PORTION; AN ELECTRIC FUZE MOUNTED IN THE REAR END OF SAID SHELL, SAID FUZE HAVING TWO EXTERNAL TERMINALS, AN ELECTRICALLY CONDUCTING CONNECTION BETWEEN SAID TERMINALS CAUSING AN ACTIVATION OF THE FUZE, ONE OF SAID TERMINALS BEING ELECTRICALLY AND MECHANICALLY CONNECTED TO SAID OUTER SHELL; AN EXPLOSIVE SHAPED-CHARGE IN THE REAR PORTION OF SAID OUTER SHELL, A GENERALLY CONICAL LINER MOUNTED IN SAID REAR PORTION OF THE OUTER SHELL COAXIALLY THEREWITH AND LINING SAID CHARGE TO DEFINE A GENERALLY CONICAL HOLLOW SPACE IN SAID REAR PORTION, THE APEX OF THE LINER FACING THE FUZE; AND A CONDUCTOR WIRE CONNECTING SAID INNER SHELL TO THE OTHER TERMINAL OF SAID FUZE, SAID WIRE EXTENDING TAUTLY STRETCHED THROUGH SAID GENERALLY CONICAL SPACE AND BEING ECCENTRICALLY DISPOSED WITH RESPECT TO THE CENTER AXIS OF THE LINER, METALLIC CONTACT BETWEEN SAID INNER SHELL AND SAID OUTER SHELL DUE TO A DEFORMATION OF AT LEAST ONE OF THE PARALLEL SIDE WALLS OF THE SHELLS CAUSING AN ELECTRICALLY CONDUCTING CONNECTION BETWEEN THE TERMINALS WHEREBY THE FUZE IS ACTIVATED. 